1. Field of the Invention
The present invention relates to a thermoplastic elastomer composition, powder or pellet of the same, and a molded article comprising the same.
2. Description of the Related Art
Hitherto, a molded article having minute uneven decorations such as leather grain and stitch on its surface is used as a skin material of an interior material of an automobile, and the like. As the skin material, a vinyl chloride resin molded article of a vinyl chloride resin or a composition comprising the vinyl chloride resin as a main component is widely known. However, hydrogen chloride gas and the like are generated when such vinyl chloride resin molded articles are incinerated after the use, and induce a problem that special incinerators are required.
As those for solving such problems, a molded article of a composition comprising a polyolefin resin and an ethylene-xcex1-olefin copolymer rubber is proposed (JP-A-05-1183 and JP-A-05-5050). However, such molded article tends to cause whitening on bending compared with the vinyl chloride resin molded article. Therefore, when the molded article is released from the mold after molding or formed into a predetermined shape, the bent portion tends to cause whitening, which results in poor appearance. Also, there is a problem that the feeling is inferior because of poor flexibility.
To solve the above described problems, the present inventors have intensively studied to develop a thermoplastic elastomer composition which scarcely causes whitening on bending and can provide a molded article excellent in flexibility. As a result, the present inventors have found that a thermoplastic elastomer composition comprising a polyolefin resin, a rubbery polymer and optionally an ethylene-xcex1-olefin copolymer rubber, having a peak at a specific peak temperature in a temperature dependence curve of tan xcex4 determined by a solid dynamic viscoelasticity measurement, does not cause whitening on bending and can provide a molded article excellent in flexibility. The present inventors have also found that a thermoplastic elastomer composition pellet having specific pellet physical properties can give a molded article having complicated shapes without causing neither pinholes nor wormholes and the resulting molded article has an excellent feeling. Thus, the present invention has been achieved.
An object of the present invention is to provide a thermoplastic elastomer composition which scarcely causes whitening and provides a molded article excellent in flexibility.
Another object of the present invention is to provide a thermoplastic elastomer composition powder or pellet which can easily give a molded article having a complicated shape and an excellent feeling, which scarcely causes whitening on bending.
Other objects of the present invention will become apparent from the following description.
According to the present invention, there is provided a thermoplastic elastomer composition comprising 100 parts by weight of a polyolefin resin, 5 to 250 parts by weight of a rubbery polymer and 0 to 500 parts by weight of an ethylene-xcex1-olefin copolymer rubber, wherein said thermoplastic elastomer composition has a new tan xcex4 peak, the peak temperature of which is different from that of the polyolefin resin and that of the rubbery polymer, at a temperature within the range from xe2x88x9270 to 30xc2x0 C. in a temperature dependence curve of tan xcex4 determined by solid dynamic viscoelasticity measurement.
According to the present invention, there is also provided a thermoplastic elastomer composition powder having the above described composition, a complex dynamic viscosity xcex7*(1) at 250xc2x0 C. of 1.5xc3x97105 poise or less and a Newtonian viscosity index n of 0.67 or less, wherein said thermoplastic elastomer composition has a specific tan xcex4 peak, the peak temperature of which is different from that of the polyolefin resin and that of the rubbery polymer, at a temperature within the range from xe2x88x9270 to 30xc2x0 C. in a temperature dependence curve of tan xcex4 determined by solid dynamic viscoelasticity measurement.
Furthermore, according to the present invention, there is provided a thermoplastic elastomer composition pellet having a sphere-reduced average diameter of 1.2 mm or less and a bulk specific gravity of at leas 0.38, which s composed of a thermoplastic elastomer composition having the above described composition, wherein a complex dynamic viscosity xcex7*(1) at 250xc2x0 C. is 5.0xc3x97104 poise or less and a Newtonian viscosity index n is 0.28 or less, and said thermoplastic elastomer composition having a specific tan xcex4 peak, the peak temperature of which is different from that of the polyolefin resin and that of the rubbery polymer, at a temperature within the range from xe2x88x9270 to 30xc2x0 C. in a temperature dependence curve of tan xcex4 determined by solid dynamic viscoelasticity measurement